Metallic thermometer



(No Model.)

' W. B. FOWLE.

METALLIC THBRMOMETER.

Patented Jan. 5 1886.

' UNITED STATES PATENT OFFICE.

WILLIAM B. FOIVLE, OF NEWTON, MASSACHUSETTS.

METALLIC THERMOMETER.

SPECIFICATION forming part of Letters Patent No. 333,738, dated January 5, 1886.

Application filed February 19, 1884. Serial No. 121,281. (No model.)

To (ZZZ whom it may concern.-

Be it known that 1, WILLIAM B. FowLE, of Newton, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Metallic Thermometers; and I do hereby declare that the following is a full, clear, and exact description of the same.

My inventi n relates to thermometers of that class in which the movement of a bimetallic strip is caused by suitable intermediate mechanism to index the temperature varia tions, and which causes greater or less flexnre, according to the degree of variation. It is more particularly an improvement upon the form of thermometer shown in the application filed by me in the United States Patent Office on the 10th day of November, 1883, Serial No. 111,451. In that application the bimetallic strip was formed into a spiral, with the sides of the strip in planes parallel with the axis of the spiral itself, was arranged with its axis parallel to the face of the dial, and in rear of the same. One end of the spiral was affixed with studs on the case, and the other carrying a crown-wheel which geared into a pinion, by means of which the motion of the spiral was communicated to the index-finger.

.The object of the present invention is to prevent the longitudinal expansion or contraction of the spiral, under increase or decrease of temperature, from crowding or too much easing the gearing and causing it to work unequally.

In this application I claim only the principle of a yielding connection between the end of the spiral and its attachments and the special means for carrying out the invention, by means of which longitudinal movement of the spiral is permitted without interfering with the crown-wheel or gearing. The construction in other respects is claimed in my aforesaid application.

In the accompanying drawings, Figure 1 shows the face of the thermometer. Fig. 2 shows aside view with the mechanism exposed. Fig. 3 shows the details of the pinion and its connection enlarged. Fig.4c is a detail view.

In order that the invention may be fully understood, I briefly describe the general construct-ion.

The face A is an ordinary dial-face, properly marked with degrees, and an index-' finger, a. on the shaft b moves over the face. The shaft is mounted in suitable bearings in a plate, F, and is provided with a pinion, c. The crown-wheel d is mounted up on the shaft 1), the inner end of which projects through the hub, and has its hearings in the inwardly-turned edge of the bridge, the other end being supported upon a pillar upon the outer end of the plate F. The crownwheel revolves around its shaft, and is retained by a stop upon the shaft 0 at a point where it meshes lightly and with the least possible friction with the pinion. The outward end of the shaft 11 has its hearings in a stem, 3, set in the pillar D. This stem has an arm, E, the outer end of which is slotted at l to receive the outer end of spiral. A setscrew, 2, serves to hold the coil in place.

In my application above mentioned the inner end of the spiral is fixed directly to the back of the crown-wheel, and when the spiral expands under increase of temperature it not only rotates, but also increases in the length of the spiral. This causes increase of friction by pressing the teeth of the crown-wheel against those of the pinion, so that at the higher temperature longitudinal expansion of the coils would retard the effect of the peripheral expansion. Under increase of temperature the spiral diminishes in length and lessens the pressure of the teeth of the crownwheel against those of the pinion. This varies the action in precisely the opposite direction. The peripheral action is alone used in the working of the apparatus. In order to utilize this peripheral expansion, I provide a plate, I, preferably circular, having a hole at its center adapted to fit snugly over the shaft b, but to permit perfectly free motion longitudinally on the shaft. The plate has also a hole or holes, 13, adapted accurately to pins is, set in the back of the crown-wheel, the plate slipping freely on said pins. The inner end of the spirial is fixed to the plate I at a distance from the back of the crown-wheel sufficient to allow the greatest possible expansion longitudinally of the spiral without causing the plate to impinge against the back of the crown-wheel. The pins prevent the plate from turning independently of the croWn- I wheel, while the longitudinal movement is perfectly free. Thus the plate connects the crown-wheel with the end of the spiral and avoids the defect before explained. The pins might be in the plate and the holes in the crown-wheel, or the plate and pins might be located at the outer end of the spiral,without departingfrom the spirit of the invention. Screws 2 and 5 serve to adjust the stem 3 to the length of the shaft b.

I am aware that other means may be used in place of plate and pins, there being many Well-known mechanical devices that may be substituted as mechanical equivalents for the means described. It would also be understood that the index-finger is set at the proper figure on the face-plate at proper adjustment in the arm E. The plate F is attached to the rear of the face-plate, as clearly shown.

I claim as my invention- 1. In a thermometer of the class described,

2. The described combination of, the spiral, 0

the means for rigidly holding it at one end, the plate attached to the spiral at the other, the wheel, and the fixed pins,substantially as described.

In testimony whereofI' have signed my name 35 to this specification in the presence of two subscribing witnesses.

WVILLIAM B. FOWLE.

\Vitnesses:

JOHN A. KENRIOK, HENRY LEMON, Jr. 

